Heating system



April 17, 1956 R. P. BUTLER 2,742,233

HEATING SYSTEM Filed 001- 4, 1951 2 Sh'ets-Sheet 1 Liam /4 if id 2 AFT INVENTOR. age); F 5 2x2 2' April 17, 1956 R. P. BUTLER 2,742,233

HEATING SYSTEM Filed Oct. 4, 1951 2 Sheets-Sheet 2 INVENTOR. ,FOZerZ )7 ,52/7/37:

HEATING SYSTEM- 'l iobert P. Butler, Birmingham, Mich, assiguor of, 28/88 to Jo' ephJ. Reader, ZZ /M88 to Albert E. Fisher, and 16/88 to Harold E. Rose, jointly Application October 4, 1951, Serial No. 249,783

' Claims. (Cl; 237-9) This invention relates to new and useful improvements in steam vacuum heating systems of the so-called onoil? type wherein steam is supplied intermittently to space heaters in the system in accordance with heat de- United States Patent 0 In conventional operation of a steam vacuum heating it system of the above type, flow of steam to the heaters usually is controlled by a valve which in turn is operated by an automatic cycling device such as a conventional thermostat or an automatic timing device which turns the steam on for a predetermined period of time and then turns it off for a predetermined time interval.

The thermostatic. control for the valve conveniently may be a conventional room thermostat which usually is mounted in a representative or key room and senses changes in the air temperature of the room, or it may be a conventional. radiator thermostat which senses changes in the temperature of a key radiator in the system. Various types of Obviously, the on and off time schedule of automatic timing devices are available. these devices must vary with the outdoor temperature. Some of these devices are manually adjustable 'to compensate forchanges in temperature and others adjust themselves automatically. In the case of a manually adjustable cycling device, the operator of the heating system notes the outdoor temperature and makes appropriate adjustments of the device from time to time. Manifes'tly, this type device requires personal supervision and almost constant attention. The automatic cycling devices adjust the time cycle of the device automatically in accordance with the outdoor temperature. These devices usually include a bulb or thermostatic element which is located outdoors and which automatically resets or adjusts the device so that it changes its cycle in accordance with changes in outdoor temperature. The thermostatic element changes the control point of the cycling dev'ice'which then continues to cycle on and oil in accordance with the temperature schedule until the thermostatic element'resets the control point in response to another change in the outdoor temperature. Automatic cycling devices are of course preferred as they eliminate the constant attention that must be given the manually adjustable cycling device.

The instantinvention can be adapted to any type onofl steam vacuum heating system regardless of the partic- 'ular control 'usedto'turn the system on and olt. The importa'nt'tlting is that some means he provided for admitting steam to the system periodically or at spaced time intervals. *R'egardles'sof the particular type control 'used, the system embodying the instant invention is operative' to open the valve to admit steam to the heaters and it makes no dilference whether it functions to open the valve whenthe temperature to which the control is s'te'n's'i'tive falls to a predetermined minimum or .in accordance with a periodic time cycle. Similarly, it makes -.line"of the system. When the absolute pressure in'the return-line rises to a predetermined maximum (usually three inches of mercury vacuum), the pump is turned on and operated continuously until the absolute pressure in the return line falls. to a predetermined minimum (usually abouteight'inches of mercury vacuum). Thus,

in conventional practice, the steam-controlvalve is operatedintermittently according, to the temperature'demands on the system and-the vacuum producer also. is operatedintermittently in accordance with the pressure conditionsin the return line of the system. In this type of conventional heating system, there is no co-ordination between the steam-control valve and the vacuum pump. Each operates independently of the other.

Steam heating systems of the above type generally are rendered ineflicient under certainconditions by accumulation of condensate at one or more places in the system and attendant natural or induced vacuum (as it is known in the trade) in the heaters and supply lines thereto. Induced vacuum is created by the system itself rather than by a vacuum produced. Induced vacuum invariably results when steam condenses in the system. The traps at the radiator outlets close when the radiators fill with steam; and when the steam valve is shut off, the entire supply side of the system is a confined space at least momentarily. Steam continues to condense in the radiators or heaters and in the supply lines of the system after the steam valve is closed, and as no additional steam is admitted to replace the condensed steam an induced vacuum is created. Further, the system continues to create an induced vacuum even after the radiator traps begin to open and as long as there is steam present that can condense in the system. In an ordinary system, an induced vacuum of from ten to fifteen inches of mercury may be produced; and if the system is exceedingly tight, an even higher induced vacuum may result. Induced vacuum prevents the condensate from draining out of the heaters, and this condensate prevents the steam from circulating through the heaters.

It is the purpose of this invention to keep steam moving through the system in one direction to and through the radiators toward the return line at all times and to keep air, non-condensable gases and condensate flowing in the same direction even when the steam valve is shut off. To my knowledge no on-ofi type of steam heating system has ever been operated before to achieve this result. This mode of operation is dilferent thanthe conventional on-oif system in which 'the steam flows to and through the radiators toward the return line only during the'on period.

As suggested, a steam vacuum heating system operated in the conventional on and oil manner has the disadvantage of uneven heating. When heat is not properly distributed among the several radiators, the radiators nearest the steam source obtain more steam than the remote radiators. This follows logically-since the entering steam fills the closest radiators and moves progressource. Also, if steam reaches all the radiators, thev ones more remote from the steam source receive steam for different periods of time. The radiators nearest the steam source arefilled withsteam for substantially the entire on period, whereas the other radiators are filled with steam for progressively shorter periods of time, depending on their distance from the steam source.

Not only will the radiators closest the steam source heat for longer periods of time but they actually contain greater amounts of steam, since the pressure is higher at this point than at more remote points in the system. By reason of the greater quantity of steam in the radiators closest the steam supply, relatively greater induced vacuum is produced in these radiators than in the more remote radiators. Since steam moves always toward the point of lowest pressure in the system, the flow of steam actually reverses when the control valve is shut off, and this reversal of movement causes the steam actually to recede from the more remote radiators. As this steam is drawn out, air andgases are drawn in through the open traps through the return line. Accordingly, if the off period is of any appreciable duration, the distant radiators go cold. By reason of this condition, the closest radiators which receive the most steam and which contain steam for the longest period of time when the steam valve is open actually rob the other more remote radiators of their steam and remain heated for a longer period ofv time when steam to the system is shut off.

Not only does incoming air cause the more remote radiators to become cold quickly but the air actually blocks the normal flow of the steam when steam is again admitted to the system. This air must be pushed back through the open traps of the radiators by the incoming steam before the steam can fill the radiators.

- The above explains why, in conventional steam heating systems of the on-olf type, remote radiators may never receive steam, particularly in mild weather, or they may heat eratically even under most favorable conditions. The above also points up the desirability of operating these systems in accordance with the present invention which maintains the steam uniformly distributed among all the radiators at all times and prevents the near radiators from obtaining more than their proportionate share ofthe steam.

In further explanation it is interesting to note that in a system which is set for full steam on at zero degrees temperature outdoors and steam off at seventy degrees temperature outdoors, the steam is on only fourteen per cent of the time when the outside temperatureis sixty degrees, twenty-one per cent of the time when the'outdoor temperature is fifty-five degrees, twenty-nine'per cent of the time when the outdoor temperature is fifty degrees, thirty-six per cent of the time when the outdoor temperature is forty-five degrees, and fifty per cent of the time when the outdoor temperature is thirty-five degrees. From the above it will be apparent that on a sixtydegree day, steam would be off for twelve minutes and on for two minutes. If the system is at all extended, two minutes is not long enough for the steam to reach the remote radiators. As a consequence only the radiators'nearest'the source of supply are heated. In. solution of the problem thus created it is not practical to increase the minimum on period sufiiciently to get steam to the far radiators because this causes the near radiators to overheat. Furthermore, an increase in the on period requires a corresponding increase in the ofi period in order to maintain the desired average temperature, and all the radiators would therefore remain cold an immoderate length of time.

Even in a fifty-degree day, the off period is approxi' mately two and one-half times as long as the on period, and in a conventional on-otf system the only movement of steam occurringduring this long off period is that caused by condensation of the steam in the radiators. This causes the radiators which are condensing steam most rapidly to rob the other radiators. As a consequence, the more favored radiators hog more than their share of the incoming steam when the control valve is again opened and the less favored radiators get less than their share or perhaps none at all.

The above condition obtains in both cold and mild weather. It is particularly aggravated in cold weather, however, when proper uniform heating is most desperately needed. As a general proposition the radiators that are still heating and condensing steam at the time the steam valve is opened exert a greater pull on the incoming steam than the radiators that have gone cold and are no longer condensing steam. In mild weather the on cycle is relatively short due to slight loss of heat from the building, and as a result of the short on phase of the cycle the thermostat may close the valve before any steam reaches the cold radiators. Thus, favored radiators overheat and the cold radiators remain cold during both cold and mild weather. In addition, pounding noises occur in the piping and heaters each operating cycle when incoming steam contacts Water of condensation held in the system, and expansion and contraction noises of piping and radiators are common due to the variation in temperature to which they are subjected and the suddenness with which these variations occur.

In conventional systems of the types described above, induced vacuum may prevent the vacuum pump from operating, and, as a result, the latter is powerless to improve the situation. In this connection it will be readily appreciated that, when any radiator 'trapin the system opens, a direct connection is established between the steam-supply line and the condensate-return line. An equal absolute pressure or vacuum is thus established at least momentarily throughout the entire system, and this pressure may be lower than the pressure for which the vacuum regulator of the pump is set. In a typical installation, for example, a pump set to begin operation when the vacuum in the system rises to three inches of mercury vacuum would not start if an induced vacuum of ten to fifteen inches of mercury existed in the system.

An important object of the present invention is to provide a method of operating an on-off type steam vacuum heating system so as to obviate the ill effects normally inherent in this type system.

Another object of the invention is to provide simple and inexpensive means for converting a conventional onoff steam vacuum heating system for more efiicient operation.

Yet another object of the invention is to provide an on-oft' steam vacuum heating system wherein all the radiators are substantially uniformly heated all the time.

Another object of the invention is to provide a steam vacuum heating system of the above-mentioned character wherein heat is distributed continuously and uniformly among all the radiators in the system even during the time when the steam-control valve is closed.

Other objects and advantages of the invention Will be apparent during the course of the following description.

'In the drawings forming a part of this specification and wherein like numerals are employed to designate like parts throughout the same: a

Fig. 1 is a diagrammatic view showing a steam vacuum heating system embodying the invention, wherein the steam supply means is at all times in direct communication with the steam-supply line of the. system and wherein operation of the vacuum pump is controlled during the initial warm-up period by the absolute pressure in the return line; v

Fig. 2 is a diagrammatic view illustrating a modified steam vacuum heating systemembodying the invention wherein flow of steam to the system is controlled by a constant differential valve;

g L Fig-r3 isa fragmentary;.diagrammatic view showing a steam vacuum heatingv system embodying: the; invention equipped with:conventional=indoor-outdoor control; and Fig. 4'is a-diagrammatic'view showing still another steam vacuum heating system embodying the; invention wherein fl ow of steamtothe; system is" controlled by a constantdiiferential yvalve and the vacuumpump is operated by a differential pressure controller. I V Fundamentally, the-instant invention ,comprises a ste vacuum .-.-heatin'gsystem wherein the steam-supply. means and thevacuum produceraare so correlated that the vacuumgproducen runs continuously to evacuate the system when and only. when the steam-supply means is shut 011' and regardless of the absolute p'ressure or'vacuum inthe system; Stated differently; the inventionlis a steam-vacuum heating: system equipped-.with amutually co-oper'ative means foroperating;- the {steam-control means and the vacuum-producer: alternately. If admissionof steam to thesystemis: controlled -by.-a-=valvle and the vacuum producer: is a pump; thepump -runs cntinuously'= during the time the valve is closed andis=stopp'edduringtthe entire time thevalve is open. It is'aprimary'feature' of thisinvention that the valve or other means forcontrolling the supply of steam to the system is operated by a -suitable. cycling device such as atherm'ostat or the like and that the pump is controlledsolely by operation of the: valve. In other words, the present invention conteme plates that steam be admitted to the system inaccordance with heat demands onthe system and that the pump be operated only when conditions are such that steam is not being. supplied tothe system. As -suggested,-.however, the pumpyis operated continuously during the time steam is shut off.

In order to explain further'theconstruction and oper ating; principles essential to the'pres'ent invention, refer: ence is first had to Fig. 1 which showsa relatively simple: heating system embodying the invention. The particular" system shown has a'stcam supply means in the form of a. boiler 10 and a burner 12 is provided for generating? steam inthe boiler. In so far as the invention is con-- cerned,-the burner 12 may be any conventional apparatus such asan oil burner, a gas burner, or a-stoker. It is pre ferred, however, that the burner be electrically controlled,1 andthe burner 12 is here shown equipped with a suitable: electrical controller 14. Current is supplied to the con-- troller 14-through electrical conduits 16 and 18 con--' trolled by'a switch 20.

Asteam supply line 22 extends from theboiler 10 to a; heat. exchanger here shown in the form of a'radiator 24.: It is contemplated that the steam supply line '22 lead& to a plurality of radiators 24;bu't in order to 'simplify'the disclosure, only one radiator is shown: The radiatorf24 is provided with the usual trap 26, and a return line 28 extends from the trap to the receiver of a condensate pump;

30: Condensate discharged from the radiator 24 through'l densatepump. 30, and when a suitable amount ofcon and energizing current is supplied to the motor-through:

electrical conduits 36,38, and 40 and starteru42. Flow of current throughconductors 36, 38, and 40 is-controlle by a switch 44- ticu-lar-lyimthe retur n "side ofthe system-so as to facilitate flow of-steam to the1radiatqr'24t Itis contemplated that the system-be operated according to conventional practice to maintain a predetermined vacuum in the return lines 28 during the initial warm-up period and-that it be converted to operate according to the present invention as soon as the indoor air reaches the temperature for which the control thermostat 62' is set. Inthe drawings the thermostat 62 is shown disposed ina key room designated 63; together with the radiator To this end, the vacuum pump 46 is provided with a vacuumregulator 64-which-is-connectedto the pipe'48' by a-pipej66. The vacuum regulator 64- is electrically connectedto the-starter 58 by electrical conductors 68 and '70 in the usual-way. As a typical example, the vacuum. regulator 64 maybe set to energize the motor and. start the pump 46 running whenever the pressure inthe return lines 28reachesthree'inchesof mercury vacuum and=to open theenergizing circuit of themotor so as to stop the pump when the pressure in the return linesreaches eight inches of mercury vacuum. Dur-ingthe beginning warm-up'period the vacuum reg-- ulator 64 maintains the circuit to the motorSt) closed until the pump 46 has reduced the pressurein the returns of the system a predetermined'amount; Inthe typical system referred to by way of example in the preceding paragraph, the pump 46 would operate until the pressure inthereturn lines had reachedeight inches of mercury vacuum. As soon-asthe pressure in the returns of the system has beenreducedsufiiciently to operate .the controller 64,'-the latter opens the circuit to the motor 50 and stops the pump 46. In the absenceof other controlling factors; the vacuumpump 46 would remain shut down until lthe pressure in-the system rose sufficiently (to three inches of ,mercury vacuum in the typical systemgiven by way ofexample above) to activate the controller 64 to again close the circuit to the' moton 50 and start the vacuum pump running: Thevacuum pumpwould' then continue to operate until thepressure in the returnlines of the system has been reduced again sufiiciently' to satisfy the controller 64. t According: tothe instant invention, however, a' relay 68 is electrically connected: to the controller 14', the starter S8, and to the thermostat 62-so as to operate the pump 46' continuously at all times when the burner 12 iS CLlt' off regardless of the pressure in the return lines 28. More specifically,-the energizing. coil 72 of relay 68 is connected in series' with the-thertnostat 62 by electrical conductors 74' and 76,- and' current is supplied thereto from any suitable source through conductors 78 and 80". The-relay 68also is provided with upper and lower pairs of contacts 82 and 84; the upper pair of contacts being connected to the controller 14 by electrical conductors 86and'88 and the lower pair of contactsbeinguelectrically connected to conductors 68 and 70 by the two conductors 9G and92. armature 94' mounted tooperate in-the coil 72 carries a switch 96 andis movable-to engage the switch with either the upper pair of contacts- 82 orthe lower pair of contacts 84'. Whenth'e' coil '72 is energized the switch 96 is' held in engagement with the upper contacts 82, andwhen' the coil 72- is deenergiz'edthe SWiiCh96 is engaged with the lower contacts 84':

a To start the system in operation, switches 20,. 44, and

are closed. Thisignit'es' the burner" 12 to produce A vacuum pump 46 is connected to the receiver of con,

,den s ate pump 30 by a pipe 48 operative to -withdraw-air and noncondensable gases from the receiver and from the conduits 52, -54,and 56 and a starter 58. A switch'60 is providedin the conduits S2, 54, and-56 to control how" of current-to the motor 50. Operationof thespu'mp46 "reducesathe absolutepressure-in the'system and parsteam in theboiler 10; energizes the motor 34 to operate the condensate pump30 and energizes" the motor 50 to operate the vacuum pump 46. Atthis time in theop crating cycle the thermostat 62' is closed, calling for more heat in the room 63; and completinga circuit through the relay coil 72 to engage switch 96 withthe upper pair of contacts 82. This closes a circuit thr'ough the controller'1'4' to maintain the burner 12 in" operation continuously until suific-ient steamhas been supplied to the radiator 24 to heat the room'163sufhcie'ntly toopen the thermostatic switch'62. When switch 62 opens it interrupts the circuit through relay coil 72 and causes the armature 94 to drop to the position shown in the drawings, opening the circuit to the controller 14 and closing a circuit through the starter 58.

Thus, de-energi zation of-the relay 68 stops the burner 12 and for all practical purposes shuts ofi the flow of steam to the heating systetm. At the same time, it closes a circuit'to the motor 50 regardless of the position of vacuum controller64 so that the vacuum pump 46 is set in operation. In normal operation of the system, these conditions obtain until the temperature in room 63 drops sufiiciently to again close the'thermostatic switch 62, at which time the latter operates relay 68 to reignite the burner 12 and again supply steam to the system and simultaneously to interrupt the circuit to pump 46 so that the latter is stopped. Thevacuum pump 46 remains inoperative during the full period when steam is supplied to the system, unless, for some reason, the absolute pressure in the return line of the system should rise sufficiently to operate the lower limit vacuum regulator 64, in which event the pump 46 operates sufficiently to. reduce the pressure in the system the predetermined amount for which the regulator is set.

This mode'of operation causes steam to be distributed substantially uniformly at all times to the radiators 24 in the system.

Assume, for example, that all the radiators 24 in the system are filled with steam at the time the steam-supply valve is closed. immediately an induced vacuum is created in the supply side of the system by the steam which condenses after the steam-supply valve is closed and water of condensation begins to accumulate in the radiators and perhaps at various other places in the system, but sinceat the same time the vacuum pump is started, it pulls from the return side of the system so as to reduce the pressure therein, and any water of condensation held up by induced vacuum is immediately released to the return line by the action of the vacuum pump and cannot interfere with continued distribution of steam during the off steam period.

As long as there is steam in the radiators and the latterare hot throughout, the thermostatic traps 26 with which the radiators are equipped remain closed, and the supply and return side of the system are maintained separate, excepting that when condensate and air form in the radiator and cool to the temperature at which the trap will function, it then opens and permits the air and condensate to pass to the return piping; however, as soon as any radiator in the system loses heat sufficiently, the trap on that radiator will open and remain open temporarily and thus permit the suction effect of the vacuum pump 46 to extend into the supply side of the system.

.This suction effect then acts to draw any steam in the system toward the trap. Since the trap is on the far sideof the radiator, the suction effect fills, or substantially fills, the radiator with steam before the steam reaches the trap. As soon as the steam reaches the trap, the latter closes to prevent steam from being drawn into the return sideof the system.

This action occurs all over the system wherever any radiator has chilled sufficiently to open the trap on the radiator. As a consequence, steam is constantlybeing pulled from the more favored parts of the system and distributed to the less favored parts even though no ad- After traps inthe system begin'toopen, the pressures in the steam supply and returnsides of the system are never far out of balance, but there is always a slightly lower pressure in the returns due to the constant action oflthe vacuum pump 46, and a positive pulling action toward the pump is always presentin the-returns. In fact, no heating system is ever absolutely tight and there is always some leakage of air into the system. Air leakage isconstantly moved toward the pump, and the moving air, however slight-in amount it may be, has a tendency to move with it'steam or any substanceientrained therein Thus these air currents, produced by leakage of air into the system, tend to assist in distributing the steam to the various radiators.

Not only does'the instant invention maintain uniform heating throughout the system but .it also keeps the thermostat satisfied for a longer period of time and, as a consequence, achieves a consequential saving in fuel and steam. This latter achievement is of course desirable under all circumstances but is particularly a factor where steam is purchased from an outside source.

Another advantage of the instant invention is that the entering steam pressure need not be as accurately controlled as .in other on-off heating systems. When the thermostat is satisfied, it operates to shut off the flow of steam to the system and immediately sets the vacuum pump in operation, thereby expanding and redistributing whatever steam was admitted and obtaining maximum benefit therefrom. .If the entering steam pressure is higher than necessary, an excess amount of steam will enterthesystem before it canbe sensed by the thermostat; thus the thermostat will then simply remain satisfied for a longer period of time while the excess steam is being condensed. On the other hand, if the steam enters at a pressure lower than the optimum pressure, the thermostat will start the burner 12 and admit more steam sooner than it otherwise would. v

From the foregoing it is apparent that induced vacuum is harmful and causes uneven heating in conventional on-otf systems, and it is particularly significant in this connectionthat operation of the on-off system in'accordance with the present invention actually utilizes induced vacuum to advantage. If an on-off steam heating system is operated in the manner herein described, induced vacuum actually assists in maintaining steam properly uniformly distributed among the several radiators in the system. In order to operate a steam heating system according to the. present invention a vacuum must be created in the system, and as a practical matter it is immaterial whether this vacuumis created mechanically by a vacuum producer or automatically by condensation ofsteam in a closedor confined portion of the system.

By reason of the fact that the instant mode of operation causes the vacuum pump to operate at the same time that induced vacuum is being created in the steam supply side of the system,.the two vacuum-producing agencies work together or in unison. Thus, if induced vacuum is being created in the system at the same time that the pump is there is no incoming air which pushes the steam out of the remote radiators and toward the radiators nearest the steam source as in a conventional on-oif system. Instead, the pump keeps the air flowing toward the pump and thus causes steam in the system to stay in the remote portions thereofand to remain substantially uniformly distributed among all'the radiators.

Further, it will be apparent that a higher vacuum can be produced in the system by using the simultaneous effect ofthe two vacuum-producing forces. it is desirable to produce a relatively high vacuum in the system since amazes 9 .it expands. the, steam, in the systemand in this manner achieves an increased efiicie ncy infoperation. The :advan.- tagetoftheating"withhighly e'panded steam will be apparentwhenv it is considered that in mild weather very little of it is, required to maintain the temperature of the space being, heated; at the desired point. In an on-ofi system operated accordingto conventional practice, howevenit has been necessary to introduce a relatively largeamount of'steam-underthese conditions in order to provide enough pressure in the system to push the steam to remote portions thereof and 'to'fill all theradiators. On the other hand,- ifthe system is operated according to the present invention a much smaller amount of. steam can be'u'ti lized during mildhveatlier. and it. is not necessary to. push. the steam into.remote parts of the system. by pressure. of the incoming steamsince the steam will be drawn into the remotepa'rtsby the pump after the steam valve has shut Qfifi The above points up clearly the advantage of operating"at'"relatively high vacuum in mild weather, and if the systemis operated according tothe present invention, high vacuum level can be reached and maintained' more easily'th'anin conventional systems whereth'e vacuum pumpis operated) and controlled merely by pressures in thesystem'. Inview of the foregoing it will be apparent that the instant'invention'will operate to distribute steamun ifo rmly amongthe radiators even though there is insuifici'ent steam in thesystem to fill all the radiators. This "isaan irnportanrconsideration, since in mild weather thisconditionmayobtaihallora large part of the time. As a consequence the'radiators'will' be onlypartially filled with steam; Under these' conditions theamountof steam in the radiators is sufiicientto maintain the surroundingair at thedesire'd temperature. In conventional steam; heatingsystems of'the on-off type it is necessary to use orifices at strategic points' in the system to force the steam to distribute uniformly throughout the system. However, this expedienthas never beenentirely satisfactory since it is diflicult to provide exactly the right" size orifices at exactly the'r-iglit points in the system. Moreover; even though propersizeorifices are provided initially; small solid particles carried into the system by thesteam s'et'tle in the orifices and"eventuallyplug them or chang e' their size-so as' to prevent them from functioning properly. The instant invention eliminates the necessity of" using orifices and therefore eliminates all the disadvantages attending useof-orific'es. .Reference isnow had to Fig. 2 which shows other means for.- controlling a steam heating system according to thepresent invention; This steam heating system'is substantially. the same asthe stearn heating system firstdescribed except.that-it includes means for maintaining a predeten mined? pressure: differential between the" steam supply; id'e' and the: return sideand-it has difl'erent means'forfco'n trollingfiow of steam into the system. For convenience andintthe interest' of brevity, corresponding parts in-tlietwo systems are identified Lby'the same referencenumeral'ss In this form of the invention no means is shown for supplying steam to the=line 22: but it willbe under-stood that the supply iline: extends from a 'suitablesource of steamyunderpressure suchas .the boileri 10 shown in Figs *1. IHEthiSyfQIHlOf the invention the 'boiler orgother-source" of; steam maintains steam under pressure available at alli times and flow of; steamqinto the heating. system is controlled by, a; constant; differential: valve 106 connected in the steamtsupply line22; The valve 1061s: opera'tedby a. conventional damper motor: (sometimes referred fo as} an electric piston) 100, and current is supplied' to*-theelectriczmotor." 112 [of piston 1 "from any suitable source through conductors 102'- and 104; The two conductor's' 86' mass 'e x'fending from the upper pair ofcont'acts 82 of relayis iare connected in series with" the motor- T12;

into engagement witli tlie'upper pair of contacts 821 Conversely, when, the thermostat 62 is. satisfied and. de energiZes relay 68,. switch 96 opens contactsand; in ten rupts tlie electricali circuit to the motor. 112 so.as;to close the valve 106 and to: shutoibflow of steam. into the. sys; tem. t

Thevalvef106 admits. steam at a rateto maintaima constant predetermined differential pressure betweemthe steam supply side and the. return side of the system. regardless, of. whether. the. absolute pressure or. vacuum in the. returnrside is high. or low. Inthis connectionitwili be observed that the constant diiferentialfvalve 1.0.6j has the usual diaphragm chamber107,;one side. of. whichis connectedto thefstearn supply line 22 bya.-pipe; 10 8.=and the other side. of which, is connected. to the, return line 28 by. a: pipe 110.: Inmostinstancesi valves, of the typ e shown at. 106, are adjustable to give diflerent differential pressures. in the system, and the differential pressure. em; ployed in. any particular instance, depends; uponthe dif? ferential required to overcome the. pressure. drop. in the systemand to. circu1ate steam to. the. remote. ends of the system. L H v t Inuatypicalinstallation thevaIVe. 10.6 maybe set to maintain a difierentialpressure. of "four inches. oflmercury. vacuum, (approximately' two pounds per. square inch.).. 113m.- this.typicalinstallation, itis assumed. that twenty inches ofl'mercury. vacuum exists. in the.return side. of the system. when. the. thermostat- 62 energizes the motor. 112,,th constantdiifetential valve. 106. regulates the. admission] of steam. to. the required pressure. differential, Thus steam. wouldenter the. system at a.pres sure ofsixteen inches. of, mercury .vacuum. Since. the vacuum pump- 46 is. shut .ofi immediately, when the valve 106 is. opened; the absolute.pressurein the returns=increases. gradually. as the steamenters. thesystem. Un; der. theseconditions the, constant: differential valve. 106. automatically compensates for the. gradually increasing, absolute, pressure. in. the returns and. admits. steam: into the, system at. a. constantly, increasing pressure, but 'always maintaining the four inches of mercury vacuum, pressure. diiferentiaL required. to. assure; proper circulation=offstean1rthroughthesystem. during; the timeuthe; vacuunipump. 46 is. shut 0th..

In-the particular arrangement. shownin the drawings the valve "106. is. shown operated. by the 1' damper motor 112 whihtisfconnected.byachain 114. tothe operating arm. .1"l6 'of,..valve..106. When the. thermostat 62 is.satis-. tied andfitscontactsare open,,the. motor.112 pulls. the: arin of ftlie steam-admissionvalve upwardly, closingofhthe. flow of. steam. Conversely, when. the thermostat 62 calls for 'heat and itsqcontactsiare.closed, themotor'. 112.releasestheoperating arm,116 and permitsthe valve to, function, ,admitting steam according to. its .setting,

The, ,advantage. of using the, differential type. valve .is. that it. willfladinit steam.- at .a rate. corresponding 2 to the, vacuum orj absolute .press'ure-in .the return line. If the. vacuum ,is" higli",, thesteamenters at, a s'lower rate-than if the ,vacuurnisllowf As;.a result, the steam does mot; enterjthe, systemrwith. a ru shasit :wouldif a-pressure re-- ducing valve were employed set for-some. positive pressure such, as-one.-.or two pounds which would be necessary, in (the coldest .we ather andwhich'would. cause -considrable ,yelocity-noiser in the milder weather whena; vacuumofisay, twentyrinch'es existed in the system. It; is obvious v that .if steam at. two. pounds .were suddenly admitteditofa system where there was. a: vacuum .of:

' twenty iiih'eis'htli'e' sudden expansion. of steam. inl-the'.

' systemwould be very noisy.

Eircep tfjfor "tl'iev foregoing, the .heating fsystemyshown; in' Fig, Ioperates in the same manner. and .achieves the same advantages as the system shown.in.Fig.. 1..

. Fi'gj yshows theradiator 24 equippedwith aconventionalf'itido'or-outdoon thermostatic control, More partieplany, theradiator hasa plurality of indoor-ole rn'eiits'i 12.0.. fastenedthereto..- An element.- 122: placed out ofdoors is connected in series with the elements-a" attests by electrical conductors 124 and 126. The two conductors 124 and 126 are connected to the usual Wheatstone bridge-type controller 127. Conductors 128 and I 130 connect the controller 127 to'the relay 68 and conductor 80 respectively, as shown. The two conductors 74'and 76 ex tendingfrom thermostat 62 are connected to conductors 128 and 130 behind the controller 126.

In practice, the control means shown in Fig. 3 can be incorporated in any system embodying the invention. If it is assumed, for example, that the control means is incorporated in the heating system shown in Fig. 2, the operation of the system is as follows:

The thermostat 62 controls the heating system during the warm-up period and therefore preferablyis located at some point indoors representativeof the temperature conditions throughout the building. When the building is cold, the contacts of thermostat 62 are closed, thus maintaining the relay 68 energized operating the damper motor 100' and holding the valve 106 open. When the temperature in the building reaches the temperature for which the thermostat 62 is set, the contacts of the thermostat open, opening the circuitto the, damper motor 100 and closing the steam supply valve 106. The controller 127 thereafter operates to hold the temperature thus established in the building. In accordance with the conventional practice the thermostat 62 operates on a differential of several degrees. Thus, when the thermostat 62 is satisfied and its contacts open, it will not again close its contacts until the temperature in the room has dropped several degrees. This permits the controller 127 to control the system after the intital warm-up and prevents the, thermostat 62 from taking control away from the controller 127. Most commercially available thermostats are adjustable to vary the differential within limits. If the thermostat 62 did not operate in this manner, opening of a window in its vicinity would cause the thermostat to close contacts and call for steam even though the controller 127 were satisfied.

When the indoor and outdoor temperatures are relatively static, the controller 127 controls the on and off cycles of the system automatically according to the temperature of the radiator 24. Thus, when the radiator 24 becomes cold, the controller 126 energizes relay 68 and opens the valve 106 to admit steam to the system. As soon as the radiator 24 warms up sufiiciently, controller126 de-energizes relay 68 and closes the valve 106 to shut 01f flow of steam to the system. Under these circumstances the steam-supply valve 106 is operated entirely by the indoor elements 120.

However, the outdoor element 122 also plays apart in the operation of the system. For example, if the out.- door temperature falls, the change is sensed by element 122 which then affects the controller 126 and 'calls for steam before the indoor elements 120 normally'would do so. Thus, the control anticipates a change'in requirement for heat and supplies additional steam to the system ,-before the requirement is actually sensed by the In this manner unicontroller vary considerably. If the systemwas con trolled solely by the room thermostat 62, the entire building would be overheated if a window were opened in the vicinity of the thermostat. Also, the indoor-outdoor controller maintains a more even temperature, since the temperature of the radiator 24 drops more quickly than' the temperature of the room, and the elements 120 attached to the radiator therefore sense the change more j quickly than the thermostat 62 which responds merely to the room temperature.

Reference is now had to Fig. 4 which shows still another steam heating system embodying the invention. This system is generally similar to the one shown in Fig. 2 but differs in that the vacuum pump 46 is not controlled directly by the thermostat 62 through the relay 68. In some installations, it may not be practical to wire the thermostat 62 directly for operation of the vacuum pump and under these circumstances the pump may be operated indirectly by a pressure controller 140 as shown in Fig. 4. in order to simplify the description, corresponding parts in Figs. 2 and 4 are identified by the same reference numerals.

In, Fig. 4 the conductors 74 and 76 leading from the thermostat 62 are connected directly to the valve 106. Thus, the thermostat opens and closes the valve 106 according to the rise and fall of the temperature in the room 63, and in the particular arrangement shown the constant differential valve 106 maintains a requisite differential between the steam supply and return lines of the system when the valve 106 is open.

In order to operate the vacuum pump '46 alternately with the admission of steam into the system, the conductors and 92 are electrically connected to the differential pressure controller 140. The latter is of conventional construction, having mechanically interconnected diaphragms in the ends thereof which act to open and close a switch connecting conductors 90 and 92 according to the difierential in pressure in steam supply and return lines of the system. In this connection it will be observed that the one end of the controller 140 is connected to the steam pipe 22 by a pipe 142 and that the other end of the controller is connected to the return line 28 by a pipe 144.

During normal operation of the system with the valve 106 closed, pressures in the steam supply and return sides of the system are substantially equal. Thus, pressure against the two diaphragms on the ends of the controller 140 is substantially equal and the switch which interconnects conductors 90 and 92 in the controller is closed. Under these conditions a circuit to the motor 50 which operates vacuum pump 46 is closed so that the vacuum pump operates continuously.

. It will be understood in this connection that while the absolute pressure in the returns may be slightly lower than the pressure in the steam supply line due to the continuous operation of the pump 46, the controller 140 is adjusted so that it will not respond to this slight differential in pressure and thus will not open the switch to interrupt the flow of current to the motor 50 which drives the pump. However, when the thermostat 62 opens valve 106 to admit steam to the system, the inflowing steam instantly increases the pressure substantially in the supply line 22, and a substantial pressure differential exists between the supply line and the return line 28. When this occurs, the unequal pressures against the diaphragms at the ends of controller 140 open the switch in the controller and interrupt flow of current to the motors 50 so as to stop the vacuum pump 46.

These relative conditions obtain in the system as long as the valve 106 is open and steam is flowing into the system. The steam of course continues to flow until the thermostat 62 is satisfied and shuts oflz' the valve 106. When the valve 106 is closed, pressures quickly equalize in the two sides of the systems, and the controller 140 again closes a circuit through the motor 50 which again drives the vacuum pump 46. The vacuum'pump continues to operate until the valve 106 is again opened by the thermostat 62.

In this installation the pump 46 will not necessarily begin to operate immediately when the valve closes. 70

V advantages as the systems first described. 3

With the exception of the above specific description, the

system shown in.Fig 4 operates exactly as, discussed in connectionwith Fig. Z'andfboth systems achievethe same advantages.v

It maythus be seen that} have. achieved. theobjects of "my invention. I have provided a steamheatingsystem wherein stcamis supplied intermittently to. radiators; or other heat-exchange means, accordingto demands on, the system and wherein. steam is. uniformly distributed throughout thesystem at all times. even when flow oflsteam to, the system is shut off. i In this manner, uniformheat ing throughout. the system is. achieved. There are no favored radiators. and. no radiator in. the. system isip er mitted to go cold. while. othenradiators. remain. heated, At; the sametime, undesirable noises. causedby. excessive expansion. andcontraction oh the. radiatorsfand piping or bi contact of steam. with. cold radiatorsforv condensate during normal. operation of the systeml-are avoided; The invention canbe readily applied. to. conventional systems andthese systems .canbe adapted toincorporatemy inventionwithvery little eifort or additional. expense.

Having thus described the invention,v I claim; 1

L. In. the operation of a steam heating system. of the type having-a: steam-supply means' for delivering steam to the systemand a vacuum producer; for exhausting air andnoncondensable gases.- from the system, the stepsconr prising controlling, the steam-supply rneans directly? as! a primary function to furnish steam intermittently to the system in accordance with the heat. demands on, the. system, andco-ordinating operation of-the vacuum producer with.thesteam supply so that the vacuumproducerropere ates. asv asecondary function subordinate to said steam supply means continuouslywhen andonly when; the sup-. ply means is shut 01f.

. ,2. In.the1operation of-a steam heating system o'fithe. type-having heat-exchange means, a steam supplyr-pipe. leading'to therheat-exchange means, a returnpipe: from. the heat-exchange means, means connected: tothe: steam: supply pipe for delivering steamto thesystem, ai -vacuuma producer connected to thereturn pipe for exhausting. air: and: noncondensable gases from the system, and thermo.-- static control; means 'operatively connected: to the stearm, supply means. to regulate admission-of. steam to;theasys.tem,;' the. steps of operating the thermostatic control; means ,tOi admit steamrperiodically to. the system in: accordance withz the=heat .demands'of the space being heated, and corntrolling operation of the vacuum producer iniaccordancet with operation of said thermostatic controlfimeans. soathat: during-normal operation of the system saidvacuumi producer-oper'ates continuously when and only: when the. steam-supply means is shut oil? by said thermostatic: C0111] p 3.. I n1 the; operationof a space-heating system: of the;

type having space heaters, steam-supply linespto=the heat: ers,-. return lines from the heaters, steam-supply means connected to the supply lines, a control valve innthe steam-supply lines and a vacuum producer connected to the return", lines, the steps of; opening the control valve periodically directly as afprimary function-rte admit steam to the system at spaced intervals and fin accordance with h'eat demands of the spacebeing heated,; and operating thevacuum producer asasecondary function subordinate to the operation of said control valve so that the vacuum producer functions continuouslyv when and only when steam is not being supplied to the system.

4. In the operation of a space-heating system of the type having space heaters, steam-supply lines to the heat ers, return lines from the heaters, steam-supply meansconnected to the supply lines, a 'valve'in the steam-supply lines controlling flow of steam into the system, a vacuum producer connected to the return lines, and a thermostatic control for said valve, the steps comprising operating said valve periodically to admit steam to the system intermittently as required by the thermostatic control, and operating the vacuum producer in accord- .ance with operation of the valve so that the vacuum pro- 1:4 ducer. operates continuously I during, the. intervals when steam to the..system,is shut ofii 5L. Iii. the -operation.of a space-heating system of the type having space, heaters, a steam-supply-line to the heaters, return lines from the. heaters, a valve on the steam-supply line for c ontrolling. flow of. steam to the system, steam-supply means connected to the supply lines,'a1'1d'a vacuum-producer connected to the return lines, the steps, of." operating saidvalve directly by. an automatic. cycling deviceto. admit. steam intermittently to the system, andtimi'ng, operation of the vacuum producer with operation of the valve so that. the vacuum producer operates, as. a secondary function subordinate to. operation of :said valve to exhaust, air. and noncondensablej gases from the system' continuously during. and only during the periodswhen the valve is. shut oh.

6, In. a space-heating system ofthe class wherein a steam-supply means furnishes. steam to space heaters. intermittently as requiredby-anon-ofri cycling device and wherein a .vacuum produceris connected to the space heaters; to maintain the system under subatmospheric pressure. and free. of air, condensate, and: noncondensable gases, the combinationfwith said Ivacuumproditcer of a control operative to lr un thegvacuuni producer as a secondary function siihordihatefto the. supply. of steam to p the system'continuously during the ofi. periods of the steam supply means. a I 7., A space-heating.systemwherein steamsupply means supplies, steam. to... spacehjeatersg in. the. system. until; anon-ofi thermostatic cycling device incorporated as a part of the system is. satisfied, wh reupon the cycling, device actslonthesteam supplymeansto shut ofl? flow of steam to thesystem until the temperature at the cycling device drops sufficiently to require adilitionarsteam in the system to raise? the temperature sufiiciently so that the. cyclingd'evice againshuts off the steam supply,means, andwherein avacuum producerfis connected to the space heaters to. maintain the system normally at a pressure lessthan atmospheric and to remove'air, condensateandf noncondensable gases from; the system; said; system being characterized by tlre'fa'ct that there is con ibinedfwithfsaid' vacuum producera control operatively connected to said cycling devicej and actuated thereby to operate theva cuunr producer continuously cluringflthe' periods when" steam to the system is shut oh? 8;. A: space-heating system "whereinsteam. is supplied tospaceheaters in the system intermittently by an electricall'y operated'steamwupply means having a thermo statically bp'era ted switch which; turns on the steam supply means to furnish steam to thespace heaters when] the temperature in the system falls to a predetermined minimumand which shuts offthe steam supply means sothatlittle ifany steam-is* suppliedtotheheaters when the'temperature in-the system reaches' a predetermined maxiinurn and 'wherein 'avacuum producer is connectedto' the space i h'eaters-ltomaintain the same relatively free frorrr-air, condensate and noncondensable. gases, said system characterized by the fact'that thereis in combination; with sai'cl ther mostatically operated switch; said vacuum: producer' and said steam-supply means, a-control connectedj in the system and operative t'o s'tart the vacuumr producer substantiallyimmediately when the i steam sup:

ply means is shut oil by said thermostatic switch, to run the vacuum producer continuously during the oif period of the steam-supply means, and to shut off the vacuum producer substantially immediately when the steam supply means is turned on by said thermostatic switch.

9. In a space-heating system of the type having space heaters, steam supply lines to the heaters, return lines from the heaters, electrically operated steam supply means connected to the supply lines, and a vacuum producer connected to the return lines, the improvement comprising temperature-sensitive means operatively conneeted to the steam supply means to operate the same intermittently as a primary function in accordance with demands on the system, and means responsive to opera- 15 tion of the steam-supply means for operating the vacuum producer as a secondary function subordinate to the supply of steamto the system continuously during the intervals when the steam-supply means is shut oil by said temperature-sensitive means.

10. In a space-heating system of the type having space heaters, a steam-supply line to the heaters, a return line from the heaters,'a valve controlling said steamsupply line and a vacuum producer connected to the return line to maintain the system substantially free from condensate and noncondensable gases, the improvement comprising temperature-sensitive means connected to the valve and operative to open and close the valve alternately in response to demands on the system, and means responsive to operation of the valve for operating the vacuum producer continuously when the valve is closedv 11. In a space-heating system of the type having space heaters, a steam-supply line to the heaters, a return line from the heaters, steam supply means connected to said steam-supply line, and a vacuum producer connected to the return line to maintain the system substantially free from condensate and noncondensable gases, the improvement comprising means for turning the steam-supply means on and off at spaced time intervals, and means controlled by said first-mentioned means for operating said vacuum producer continuously during the time the steam is shut off.

12. In a spaceheating system of the type having space heaters, a steam-supply line to the heaters, a return line from the heaters, steam-supply means for supplying steam to the heaters through said steam-supply line, a vacuum producer connected in said return line operative to keep the heaters substantially free from condensate and noncondensable gases, and a'thermostatic control for operating the steam-supply means intermittently in accordance with demands on the system, the improvement comprising means operatively connected to the thermostatic control and to the steam-supply means to admit steam to the system when the temperature reaches a predetermined minimum and to shut off steam to the system when the temperature reaches a predetermined maximum, and means sensitive to conditions in the system for operating said vacuum producer continuously when the steam supply to the system is shut off. 2

13. In a space-heating system of the type having space heaters, a steam-supply line to the heaters, a return line from the heaters, steam-supply means for supplying-steam to the heaters through said steam-supply line, a vacuum producer connected in said return line operative to keep the heaters substantially free from the condensate and noncondensable gases, and a thermostatic control for operating the steam-supply means intermittently in accord ance with heat demands on the system, the improvement comprising means operatively connected to the thermostatic control and to the steam-supply means to admit steam to the system when the temperature reaches a predetermined minimum and to shutoff steam to the system when the temperature reaches a predetermined maximum, and a control sensitive to conditions in the system for operating said vacuum producer continuously 6 when the steam'supply to the system is shut off, for

Utu

. connected to the supply line for controlling flow of steam to the heaters, an electrically operated vacuum producer connected in the return line to maintain the heaters free from condensate and noncondensable gases, and a ther mostatic switch operatively connected to said steam-supply means for'supplying steam to the system intermittently in accordance with heat demands on the system, the improvement comprising a relay electrically connected to said thermostatic switch, said steam supply means and said vacuum producer operative to shut ofl the vacuum producer each time the steam-supply means is operated by said thermostatic switch to supply steam to the heaters and to start the vacuum producer in operation to evacuate the return line of the system each time the steamsupply means is shut ofi by'said thermostatic'switch.

15. In a space-heating system of the type having space heaters, a steam-supply line to the heaters, a return line from theheaters, electrically operated steam-supply means connected to the supply line for controlling flow of steam to the heaters, an electrically operated vacuum producer connected in the return line to maintain the heaters free from condensate and noncondensable gases, and a thermostatic switch operatively connected to said steam-supply means for supplying steam to the system intermittently in accordance with heat demands on the system, the improvement comprising a relay having an energizing coil and two pairs of contacts, the energizing coil being connected electrically in series with said thermostatic switch, one pair of contacts being connected in series with the control circuit of the electrically operated steam-supply means, and the other pair of contacts being electrically connectedto the control circuit of the electrically operated vacuum producer, the arrangement being such that thethermostatic switch closes to energize the relay coil when the temperature in the system falls to a predetermined minimum, and energization of the relay coil closes the contacts in the control circuit of the steam supply means and opens the contacts to the vacuum producer so that steam is supplied to the system and the vacuumproducer is shut off, and whereby opening of thehthermostatic switch caused by a predetermined temperature rise in the vicinity of the switch de-energizes the relay coil, opens the contacts in the control circuit of the steam-supply means and closes the contacts in the control circuit of the vacuum producer so as toshut ofi steam to the system andstart the vacuum producer in operation. J.

7 References Cited in the file of this patent UNITED STATES PATENTS 2,312,192 Reader Feb. 23, 1943 Jennings Dec. 3, 1940 

